In general, three-dimensional (3D) imaging (or stereoscopic imaging) depends on the principle of stereovision. The stereoscopic effect is primarily based upon binocular parallax, which is the distance, on average about 65 mm in humans, between a pair of eyes. Each of the left and right eyes view a separate planar image and the brain combines the two separate images into a 3D image to thereby give a sense of depth and a sense of reality.
3D display technologies are largely classified into three types: stereoscopic, volumetric and holographic. In a stereoscopic 3D display, for example, depth information is added to a two-dimensional (2D) image so that an observer is tricked into perceiving a 3D image with a sense of depth and a sense of reality. Holography offers the potential to create true 3D images that have all the human visual system depth cues of a natural object.